Radio transmission system



E. W. KELLOGG RADIO TRANSMISSION SYSTEM Jan. 12 ,1926.

Filed Jan. 1925 [724 AMP 2.95 am: 4/4 "g AMP 1m" 2420 OHHS I000 0/1376 9QZ :3 o r Win u M v s .3 H W m Patented .Jan.-.12, 1926.

1 UNITED STATES.

EDWARD W. KELLQ GG, OF SGHENECTADY,

PATENT. OFFICE.

NEW YORK, ASSIGNOR TO GENERAL ELEG- TRIO COMPANY, A GQRPORATION or NEWYORK.

RADIO TRANSMISSION SYSTEM.

Application filed J aniiary ticularly to transmitting systems of thedirective type.

It has been proposed to employ a pluralityof individual radiating'unitsarranged in a row and by proper adjustment of the phase relation of thecurrents supplied to the different units to produce radiation, the

reater part of which will be effective only in one of, the directionsbetween which the row extends.

One of the objects of my present invention is to provide a simple andeffective means for supplying currents to the different radiatingunitsin a system of the class described in such a way that the phaserelations between the different currents will be those necessary forproducing the desired directive effect.

In attaining this object of my invention, I provide a singletransmission line for supplying currents to all of the radiating units.For producing the desired directive effect the radiating units should beseparated from. one another by distances of the order of a quarter wavelength and the currents in the different units must differ in phase bysimilar fractions of a cycle. If the transmission line is so constructedthat waves are propagated thereon at substantially light velocity thebase differences of the currents supplied at t e different feedingpoints along its length will be correct for a unidirectional system.This will be true, however, only in case there are no reflections overthe line from the .feed points and the line carries waves in onedirection only. If a number of loads are connected to a transmissionline either as shunt or series loads, reflections will result and theproper phase "relations will not be secured.

A more specific; object of my invention is to provide, means wherebycurrent may be.

supplied from a transmission line at a plura ity of points along itslength without producing any reflections.

so, 1925. Serial No. 5,737.

Inattaining this object of my invention I provlde means at each feedingpoint wherer by the loadsare a combination of shunt and series loads. Byproper proportioning of the shunt and series loads in a manner whichwill be more fully described, .I am able to prevent reflections over thetransmission line.

In the case of directive transmission it is desirable that equalcurrents be supplied to all of the radiating units. In case enough unitsare used to, provide very sharp directivity the last units to besupplied will not, on account of line attenuation receive the dueproportion of the total energy supplied unless suitable precautions aretaken. .7

Still another object of my invention is to provide means whereby theenergy supplied y the transmission line will be equally divided amongthe different radiating units.

This object may be attained by suitable proportionin of the loadresistances at the different fee ing oints in a manner which will alsobe more ully described.

The novel features which I believe to be characteristic of my inventionare set forth with partioularit in the appended claims; my inventionitse f, however, will best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFigs. 1 and 2 are diagrammatic. representations of networks havingsuitable constants for obtaining the results of my invention, and Fig.3is a diagrammatic representation of the application of my invention toaradio transmitti-ng system. v Thenormal high 'efliciency unloaded linehas a characteristic or surge impedance which is practically equivalenttoa pure to construct afladder type network of SQ:

rice and shunt resistances which has the same characteristic impedance,as the transmission line. The transmission line may then be cut and asmany sections of this network as desired introduced and no reflectionswill result, but attenuation will take place in the resistance network,depending on'the number of sections introduced, or on the ratio ofseries to shunt resistance. By this means any desired fraction of thepower carried by t the line may be absorbed in a local network,

and not give rise to reflections. It h attention;

nation per section is small, say not over 20% reduction in current, thefollowing relations hold:

in which R is the series resistance per sec- R is the shunt resistanceper section;

Z is the line surge resistance;

K is the ratio of the current on the two sides of a section or thesquare-root of the ratio of power received to power passed on.

If each section is a T network (i. e., two equal series resistances andone shunt resistance), as much as 50% of the power may be absorbed in asingle section, the above formulas may be used without material error.Assume, for example, that the hue surge resistance is 1000 ohms and that11: is desired to use up equal amounts of power at a series of points,A, B, C, etc. Fig. 1 represents a line with a series of networksintroduced. The losses in the line itself are neglected. At the end, A,the load reslstance must be equal to Z or 1000 ohms 1f reflection is tobe avoided. Taking the current at A as 1 ampere the power absorbed willbe 1 k. w. An equal amount of power must be absorbed at B or powerreceived- ,IR R, 1000 The network at G is to receive 3 k. w. and pass on2 k. w., whence K z3/2,

I Thevoltages and currents, calculated step by step, are shown onFig. 1. It is seen that the interposition of one of the T networksleaves the ratio of voltage to current prac- The series resistances canbe divided between the two sides of the line to give balance.

The networks might consist of simple L sections, but in this case adifferent formula is-required. If the forward moving wave encountersfirst the series resistance R, and then the shunt resistance R, as inFig. 2.

in which K is the current ratio on the two sides of the network, or thesquare root of the power ratio.

In order to apply the principles above outlined to the feeding of aseries of radiating units the units must be coupled to the transmissionline in such a way that they become the equivalent of pure resistanceloads the values of which depend upon the mutual inductance of theprimary and secondary circuitv In the arrangement shown in Fig. 3 I haveindicated a method of coupling which may be made to give a load on thetransmission line analogous to that represented in the network ofFig. 1. In this case the transmission line having conductors 1 and 2 issupplied with current from a high frequency source 3. Energy is suppliedfrom the transmission line to a series of radiating units 4 to 8, whichin the case illustrated are represented as vertical conductors havingboth ends insulated from ground. Each unit except 8 is coupled to thetransmission line by series coupling transformers 9 and 10 and a shuntcoupling transformer 11. The last unit 8 requires only the singlecoupling transformer 12. In the absence of reflected waves the currentthrough the series coils and the voltage across the shunt coil are inphase. It the latter constitutes a resistance load the current throughit will be in phase with that through the series coils. Under thesecircumstances both can be coupled to the same secondary circuit and eachcan be made to contribute its share to the power in the secondarycircuit.

'What I claim as new and desire to secure by Letters Patent of theUnited States, 1s:- a

1. The combination in a radio transmitting system of a radiating systemcomprising a plurality of radiating units separated from one another byan appreciable fraction of a wave length of the waves to be radiated, asingle transmission line for supplyin to said radiating units currentshaving p ase displacements corresponding to the geographical dislacements of the units from one another, an means for preventing wavereflections over said transmission line from 1,5ee,sss

the points ,at which energy is supplied to the radiating units.

2. The combination in a radio transmitting system of a radiating systemcomprising a plurality of radiating units separated from one another byan appreciable fraction of a wave length of the waves to be radiated, asingle transmission line for supplying to said radiating units currentshavplyingto said radiating units currents having p ase displacementscorresponding to the geographical displacements of the units from oneanother, means for preventing wave reflections over said transmissionline from the points at which energy is supplied to the radiating units,and means for roducing a substantially uniform. distrlbu-- tion of powerto all of said radiating units.

4. The combination in a radio transmitting system of a radiating systemcomprising a plurality of radiating units separated from one another byan appreciable fraction of a wave length of the waves to be radiated, asingle transmission line. for supplying to said radiating units currentshaving phase displacements corresponding to. the geographicaldisplacements of the units from one another, and means for feedingenergy to said radiating units by both series and shunt transformerconnections to said transmission line.

5. The combination in a radio transmitting system of a radiating systemcomprising a plurality of radiating units se arated from one another byan appreciab e fraction of a wave length of the waves to be radiated, asingle transmission line for supplying to said radiating units currentshaving phase displacements corresponding to the geographicaldisplacements of the units from one another, and means for feedingenergy to said radiating units by both series and shunt transformerconnections to said transmission line, said transformer connectionsbeing so proportioned that the power supplied by the transmission linew1ll be substantially uniformly distributed among the difl'erentradiating units. a

6. The combination in a radio transmitting system of a radiating systemcomprising a plurality of radiating units separated from one another byan a preciable fraction of a wave length of t e waves to be radiated, asingle transmission line for supplying to said radiating units currentshaving phase displacements corresponding to the geographicaldisplacements of the units from one another, and means for feeding

